Method for carrying out pyrolysis

ABSTRACT

The invention relates to a method for carrying out pyrolysis in such manner that a first raw material is fed to a combustion boiler and a second raw material is fed to a pyrolysis reactor which are integrated together, energy fractions are formed from the raw material in the combustion boiler and gaseous and liquid product fractions are formed from the raw material in the pyrolysis reactor by fast pyrolysis. According to the invention, production of the pyrolysis product and energy fractions is controlled by optimizing the selection of the raw material, product distribution and production costs, value and quality of at least one product fraction by varying the process variables, which are selected from the group comprising a first raw material, a second raw material, quantities of the raw materials, selection of additional materials, process parameters, selection of an additional process step, composition and quantity of the carrier gas used, quantity of oxygen, selection of the heat transfer agent and moisture content of the raw material.

FIELD OF THE INVENTION

The invention relates to a method defined in the preamble of claim 1 for carrying out pyrolysis in such manner that a first raw material is fed to a combustion boiler and a second raw material is fed to a pyrolysis reactor which are integrated together, energy fractions are formed from the raw materials in the combustion boiler and gaseous and liquid product fractions are formed from the raw materials in the pyrolysis reactor by fast pyrolysis.

BACKGROUND OF THE INVENTION

It is known from the prior art that a pyrolysis product, i.e. pyrolysis liquid or pyrolysis gas, is produced from different kinds of biomasses or organic materials such as wood, bark, paper, straw, waste plastic, oil shale, lignite, peat or the like by dry distillation with the pyrolysis technique. The pyrolysis is typically performed in oxygen-free conditions at a temperature of about 300 to 800° C. When slow heating rate is applied, the pyrolysis liquid, e.g. wood tar from dry wood, can typically be recovered in an amount of about 20 to 30% by weight. The amount of the pyrolysis liquid increases when the fast pyrolysis method is applied. There are many known fast pyrolysis methods for producing pyrolysis products and chemicals.

Fast pyrolysis is typically carried out by heating the fuel to be pyrolyzed in a hot oxygen-free gas flow by introducing the required heat to the pyrolyzer by means of a heating gas, heat exchanger or heat transfer agent, e.g. sand or aluminum oxide based carrier. A bubbling or sand circulating fluidized-bed reactor may be used as the pyrolyzer. The produced pyrolysis steam is condensed to a temperature of less than 150° C. to form the pyrolysis liquid.

The fuel to be pyrolyzed, e.g. biomass, may be conducted to a dryer before the pyrolyzer for drying in order to reduce the water content of the pyrolysis liquid that is being formed. Normally used are the known drum, flash or fluidized-bed dryers which typically comprise combustion gas or water vapor as the drying gas. It is also known to use a steam dryer in which the heat is introduced by means of hot sand to the dryer operating on the fluidized-bed basis and in which only water is removed. The temperature is kept at such level that organic compounds do not escape. EP publication 513051 (Ensyn Technologies Inc.) describes a method and apparatus for producing a pyrolysis liquid from fuels by fast pyrolysis in such manner that the circulating mass reactor which operates as the pyrolyzer comprises separate mixing and reactor zones. The heat transfer to the fuel particles is effected by using heat transporting sand or an alumina-silica catalyst having the average particle size from 40 to 500 μm as the heat transfer agent. The method uses an oxygen-free carrier gas. The feeding material in particle form, oxygen-free carrier gas and hot heat-transporting particle material are mixed together in the base section of the reactor, and the mixture is transported upwards to a reactor section in which the feeding material is converted to products. The contact time between the feeding material and the heat transporting material is less than 1.0 seconds. The heat transporting particle material is separated from the product fractions and recirculated to the reactor. In the method, the mass ratio of the heat transfer material to the fuel is greater than 5:1.

Also known from prior art is the use of an oxidizing reactor for processing sand that exits the pyrolyzer and coke produced during the pyrolysis. In the oxidizing reactor, coke is burned and sand is heated and recirculated to the pyrolyzer. The ratio of the oxidizing reactor power to the pyrolyzer fuel power is typically 1:5. This type of oxidizing reactor is designed to primarily burn only the coke produced during the pyrolysis and the non-condensible gases. Therefore, the heat content of the coke and non-condensible gases is, by the energy balance, a limiting factor in the mass feed to the pyrolyzer.

A problem with the known pyrolysis processes is the need for additional fuel in the pyrolyzer and in the additional equipment, such as the dryer, and the possible drifting of the water that has been vaporized in the process to the pyrolysis oil. Normally, the water vaporized for example in the dryer is condensed or conducted to outside air. When the vaporized water contains organic dry distillation products, application of the process becomes problematic due to environmental nuisances, e.g. strong odors. Further, the known devices do not permit utilization of different process flows, side flows and unwanted intermediate/end products in the process in an efficient manner.

Furthermore, it is previously known from patent FI 117512 by the same applicant to integrate the pyrolyzer and the combustion boiler to one assembly.

OBJECTIVE OF THE INVENTION

The objective of the invention is to eliminate the above-mentioned problems and to disclose a novel method for use in carrying out pyrolysis and different ways of running the pyrolysis, and in optimizing the pyrolysis and energy product distribution. One specific objective of the invention is to disclose a method for producing simultaneously heat energy and a pyrolysis product in an industrial scale and environmentally friendly manner by circulating and utilizing the process flows that are produced during the process.

SUMMARY OF THE INVENTION

The method according to the invention is characterized by what has been presented in the claims.

The invention is based on a method for producing pyrolysis and energy products in a flexible manner and for carrying out and enhancing the pyrolysis in such manner that a first raw material or mixture of raw materials is fed to a combustion boiler and a second raw material or mixture of raw materials is fed to a pyrolysis reactor, which are integrated together, energy fractions are formed from the raw materials in the combustion boiler in the form of heat, electricity, steam or gas, and gaseous and liquid product fractions are formed from the raw materials in the pyrolysis reactor by fast pyrolysis. According to the invention, production of the pyrolysis product and energy fractions is controlled by optimizing the raw material and the selection thereof, such as availability, costs and quantity, product distribution and production costs, value on the market and quality of at least one product fraction, preferably the production costs, value on the market and quality of a number of product fractions, by varying the process variables, preferably more than one process variable, which are selected from the group comprising a first raw material, second raw material, quantities of the raw materials, selection of additional materials, process parameters, selection of an additional process step, composition and quantity of the carrier gas used, quantity of oxygen, selection of the heat transfer agent and moisture content of the raw material.

In this context, the first raw material refers to a raw material or a mixture of raw materials to be fed to the combustion boiler. In this context, the second raw material refers to a raw material or a mixture of raw materials to be fed to the pyrolysis reactor. The first and the second raw material may be identical, partly similar or completely different in composition. In one embodiment, substantially different raw materials are fed to the combustion boiler and the pyrolysis reactor in order to maximize the efficiency ratio between the combustion and the pyrolysis and yield of the pyrolysis product.

In the method according to the invention, the process is preferably run systemically by optimizing the raw material to be selected, the product distribution, the quantity and quality of the product. In one embodiment, the proportion of the most valuable product fractions is maximized.

Preferably, the integrated combustion boiler supports the carrying out and success of the pyrolysis.

In one embodiment of the invention, the raw materials, which are in the form of a solid, liquid, vapor or gas, are selected from the group comprising organic matter, chips, forest chips, wood, bark, sawdust, straw, coal, peat, oil, oil shale, lignite, petroleum, biomass, energy containing waste material, plastic, waste plastic, fuel containing waste, refuse derived fuel/RDF, pine oil, black lye, organic solvent and derivatives thereof. In one embodiment, the raw material or raw materials may be selected e.g. from adjacent containers, depending on what kind of product distribution is desired.

In one embodiment, the energy and pyrolysis product fraction, which is in the form of a solid, liquid, vapor or gas, is included in the group comprising pyrolysis gas, pyrolysis steam, pyrolysis liquid, pyrolysis oil, black lye, pine oil soap, fuel, chemicals, carbon fiber, liquefiable tar, gasification gas, burnable gas, steam, water vapor, hydrogen, heat and electricity.

In one embodiment of the invention, the gaseous product fractions which are produced during the pyrolysis are condensed to mainly liquid pyrolysis products. In one embodiment, most of the energy and pyrolysis product fractions are circulated, recovered, processed further and/or utilized.

Preferably, only part of the energy fractions that have been formed in the combustion boiler are conducted to the pyrolysis reactor and other process steps.

In one embodiment of the invention, a heat transfer material is used for transferring the energy fraction, preferably heat, from the combustion boiler to a desired process step, e.g. pyrolysis or the desired and predefined additional steps and/or recovery. In one embodiment, the heat transfer material is conducted separately to each process step. In an alternative embodiment, the same heat transfer material circulates through different steps. In one embodiment of the invention, heat transfer material is circulated from the combustion boiler to the pyrolysis reactor and from the pyrolysis reactor back to the combustion boiler via a separation step.

In one embodiment, the heat transfer material is selected from the group comprising sand, bed sand, aluminum oxide based material, other fluidization material and the like.

In one embodiment of the invention, the method comprises a multistep pyrolysis in which fast pyrolysis is performed as a first step and improved product fractions and/or additional product fractions are formed as a second step by applying an additional step.

In one embodiment of the invention, the method comprises a multistep pyrolysis in which an additional step is performed as a first step and fast pyrolysis is performed as a second step in order to form improved product fractions and/or additional product fractions.

In one embodiment, the additional step is selected from the group comprising: drying, raising the temperature, gasification, dust separation, reforming, steam reforming, separating the product fractions and separating the solids. The separation of solids may include separation of the heat transfer agent, such as sand, carbon matter, coke, solid particles or equivalent solids.

In one embodiment, the first and the second step are substantially integrated to one assembly, e.g. one device. In an alternative embodiment, the devices of the first and the second step are connected together.

In an alternative embodiment, the multistep pyrolysis may include more than two steps.

In one embodiment of the invention, carrying out of the pyrolysis step is modified in the method by at least one special operation which is selected from the group comprising raising the temperature, reducing the temperature, selecting the carrier gas, feeding steam and adding oxygen.

In one embodiment, the pyrolysis gas that has been formed in the first step is conducted to the second step in which the temperature is substantially higher than in the pyrolysis step. If water vapor is used as the carrier gas in this second step, a steam reforming reaction occurs, resulting in a large proportion of the tar compounds decomposing to hydrogen and carbon monoxide.

In one embodiment, the heat transfer agent is fed to the reactor in two steps, to a drying step and to a reaction step. The temperatures of the drying step and the reaction step are adjusted separately for optimizing the product distribution and quality of the product. In one embodiment, the raw material that has been fed to the drying step and the heat transfer material are conducted as a mixture to the second step, i.e. the reaction step, after drying.

Any drying method known per se may be used as the drying method, e.g. low temperature drying, drying by mixing or the like. Part of the heat energy that has been formed in the combustion boiler can be utilized for drying the fuel to be pyrolyzed. By drying, the water content of the pyrolysis product that is being formed is preferably reduced, whereby the stability of the product increases. Water vapor can be recovered from the drying and be utilized e.g. in heat production. In one embodiment, the vapor is not separated from the drying step.

In one embodiment, the pyrolysis reactor is run as a gasifier-type device. In this case, the temperature in the reactor is higher than in the normal pyrolysis, and the gas yield is maximized in the product distribution. In one embodiment, natural gas is fed to the reactor as the additional material.

In one embodiment of the invention, the carrier gas is selected from the group comprising combustion gas, preferably purified combustion gas, water vapor, air and a mixture thereof.

In one preferred embodiment of the invention, the carrier gas contains oxygen. Preferably, the pyrolysis is performed in the pyrolysis reactor in the presence of oxygen. In one embodiment, carrier gas that contains oxygen in an amount of 1 to 7% by volume is used. The preservability of the pyrolysis product can be increased by the use of oxygen.

In one embodiment, additional oxygen is added to the carrier gas e.g. in the form of air, to increase the oxygen content.

In one embodiment, purified combustion gas from the combustion boiler is used as the carrier gas and circulated from the combustion boiler to the pyrolysis reactor.

In one embodiment, water vapor is used as the carrier gas. In this case, a steam reforming reaction occurs, resulting in a large proportion of the tar compounds decomposing to hydrogen and carbon monoxide.

In a preferred embodiment, the carrier gas is conducted once through the pyrolysis reactor and conducted to the combustion boiler. The carrier gas is not recirculated from the outlet of the pyrolysis reactor to the inlet of pyrolysis reactor.

In one embodiment of the invention, the process parameters are selected from the group comprising the temperature of the pyrolysis step/temperature in the pyrolysis reactor, temperature of the additional step, residence time in the pyrolysis reactor, temperature of the combustion boiler, way of mixing and order of mixing of the raw materials of the pyrolysis, carrier gas and heat transfer material, addition of oxygen, circulation of the heat transfer material and circulation of the product and side fractions.

In one embodiment, the product fractions which are being formed in the combustion boiler and pyrolysis reactor are divided into products, side flows of the process, residual flows, waste flows and/or unwanted fractions. In one embodiment of the invention, most of the side, residual and waste flows, e.g. residual flows from the condenser, residual flows from the separating devices and filters, refuse flows of the raw materials, combustion gas fraction and the equivalent flows, are substantially circulated to the combustion boiler. Feeding the side, residual and waste flows and the feed volumes thereof to the combustion boiler do not have to be adjusted separately, due to the substantially larger raw material feeding of the combustion boiler itself.

In one embodiment of the invention, the first raw material and the carrier gas are arranged to a mixture and the heat transfer material that has been heated is conducted to the mixture.

In one embodiment, suitable additional materials are used in different steps of the process. E.g. alcohols, such as isopropanol, ethanol or rapeseed oil methyl ester, can be used as additional materials in conjunction with the condenser to improve the operation of the condenser and/or quality of the product. Alcohol-based materials can also be used in conjunction with washers or the like to improve the operation of the device. In one embodiment, catalysts can be used as additional material, e.g. in the pyrolysis reactor or combustion boiler, e.g. in conjunction with the sand circulation, to improve the efficiency of the process and/or quality of the product.

Thanks to the invention, the efficiency, costs and product distribution of the process can be optimized with respect to the price of different products and product quality requirements. The invention provides the advantage that the combination of the pyrolysis and combustion according to the invention can be utilized in the production of different and new products. Thanks to the optimization method according to the invention, the pyrolysis reactor may also serve at least partly other purposes than the usual pyrolysis in terms of capacity and time. Furthermore, different additional steps and devices can be readily combined with the pyrolysis reactor in order to control the product distribution. The integrated solution according to the invention provides a wider operational framework for different ways of running and producing different products.

The pyrolysis product and the energy fraction can both be produced by the method according to the invention with higher efficiency than what is known, because the side and waste flows which are being produced, solid and carbon matter and non-condensible gases and energy content thereof can be converted in the combustion boiler to heat or steam for energy production. Part of the heat energy of the combustion boiler is used in the pyrolysis reactor, optionally for drying the pyrolyzed fuel and for other additional process steps and for combustion of the non-condensible gases in the combustion boiler, and most of the heat energy is conducted to be recovered e.g. in the form of steam. Additional feeding of energy is not required for the pyrolysis reactor and for other process steps, because the heat energy conducted from the combustion boiler is sufficient for maintaining the process. The invention provides the advantage of achieving self-sufficiency in terms of energy by the combination of the pyrolysis reactor and the combustion boiler according to the invention.

Feeding the optimal fuel mixtures to both pyrolysis reactor and combustion boiler improves the efficiency of the process in terms of yield of the pyrolysis product and heat energy and minimizes the process costs.

The method according to the invention is easy to carry out in the production. Thanks to the integrated combustion boiler, energy is available and e.g. the temperature of the pyrolysis reactor can be easily adjusted. The method according to the invention can be applied for pyrolyzing a product utilized from any suitable raw material. Furthermore, management of the process according to the invention is easy. Coke and other equivalent residual fractions do not accumulate in the process equipment but can be instead conducted to the combustion boiler to be burned, so that they do not cause any problems in the process. Therefore, the possible coke content of the raw material does not have to be concerned about when selecting the raw material.

A further advantage of the invention is that the coke balance of the process and the heat balance of the drying do not provide a restriction for the pyrolysis and other process steps.

DETAILED DESCRIPTION OF THE INVENTION

In the following section, the invention will be described with the aid of detailed exemplary embodiments.

Example 1

The process assembly according to the invention is formed, comprising a combustion boiler, pyrolysis reactor and condensing device. The pyrolysis reactor and the condensing device are substantially integrated with the combustion boiler, i.e. a unified assembly is formed. Fuel is fed to the combustion boiler and burned for producing heat energy. In the pyrolysis reactor, gaseous pyrolysis products are formed from suitable raw materials by pyrolysis and condensed to liquid pyrolysis products in the condensing device. Carrier gas is fed to the pyrolysis reactor. The energy fractions in the form of heat, water vapor or gas, formed in the combustion boiler, are recovered or part of the heat is circulated to the other parts of the apparatus, such as to the pyrolysis reactor, in the form of a hot heat transfer agent, which in this embodiment is bed sand.

Example 2

The method of this example is carried out by the process apparatus according to Example 1.

In the method, the most valuable and suitable part of the raw material is used as the pyrolysis material and the less suitable part in terms of pyrolysis is fed to the combustion boiler. The raw material is divided in a manner known per se, e.g. by a classifier or optical separator.

Good raw materials for the pyrolysis include residuals from the forest industry, such as chips, saw dust and bark chips. However, high liquid yield is only obtained for dry raw material from the so-called heartwood without bark. In other words, a lesser amount of the pyrolysis product is produced from the bark which is furthermore more unstable and easily phase-separated. Therefore, it is not advisable to feed the same raw material to the pyrolysis reactor and the combustion boiler. A preferred embodiment is to conduct bark containing raw material to the combustion boiler to produce energy, and saw dust to the pyrolysis reactor to produce a pyrolysis product. In addition, e.g. peat or coal is conducted to the combustion boiler to satisfy the entire fuel need.

Example 3

The method of this example is carried out by the apparatus according to Example 1. In this example, the processing includes two steps, and the steps are combined together.

The pyrolysis gas that has been formed by pyrolysis in the first pyrolysis step is conducted to the second process step in which the temperature is substantially higher than in the pyrolysis step. If water vapor is used as the carrier gas in this second step, a steam reforming reaction occurs, resulting in a large proportion of the tar compounds decomposing to hydrogen and carbon monoxide. This method enables the production of gasifying gas e.g. for the Fischer-Tropsch synthesis.

Example 4

The method of this example is carried out by the apparatus according to Example 1.

Water vapor is used as the carrier gas in the pyrolysis. The vapor may be obtained from the humidity of the raw material which is separated e.g. during drying of the raw material. A steam reforming reaction occurs. The product is a burnable gas or one that can be processed further chemically, such as ammonia or a synthetic fuel. The product gas may be used e.g. in the Fischer-Tropsch synthesis. The humidity of the raw material can be utilized as the steam in steam reforming.

Example 5

The method of this example is carried out by the apparatus according to Example 1. In this example, the process includes two steps and the drying and reaction processes are combined together.

The heat transfer agent, which is bed sand, is fed in two steps, the first part to the drying step and the second part to the reaction step. The temperatures of the drying step and the reaction step are adjusted separately for optimizing the product distribution and quality of the product. Vapor is not separated from the drying step but instead from the condensing of the product gas.

Example 6

The method of this example is carried out by the apparatus according to Example 1.

In this process, the raw material for the pyrolysis reactor and the carrier gas which is a purified combustion gas are arranged to a mixture and the hot bed sand particles from the combustion boiler are conducted to the pyrolysis reactor to the mixture of the raw material and the carrier gas. In this case, an area of heavy turbulence is formed at the mixing point, i.e. a so-called flash effect occurs, whereby the pyrolysis can be initiated rapidly and efficiently. The applied sand, which in this embodiment has a grain size of more than 0.5 mm, is substantially heavier than the raw material of the pyrolysis and, therefore, acceleration of the sand particles induces more efficient heat transfer and mixing of the gases in the mixture flow, resulting in an enhanced pyrolysis.

Example 7

The method of this example is carried out by the apparatus according to Example 1.

By increasing the proportion of air and thereby the oxygen content in the carrier gas, the proportion of the liquefiable components in the pyrolysis product, relative to the proportion of the non-condensible fractions, can be varied according to the desired product distribution. In this manner, the pyrolysis reactor can be used as a gasifier-type device. The efficiency and heat value provided by the combination of the pyrolysis and the combustion boiler for the gas are higher than in the traditional air gasification, because most of the heat can be introduced to the gasification reaction by the circulating mass, i.e. the bed sand.

Example 8

The method of this example is carried out by the apparatus according to Example 1.

The product gas produced in the pyrolysis is heated to a temperature above 1000° C. to decompose the hydrocarbons. As a result, hydrogen and carbon are produced as products in the form of fine fibers. Due to their high strength, these carbon fibers can be utilized as additional material e.g. in papermaking. The advantage of the method is the inexpensive process for producing carbon fibers, utilization of biomass in the production of carbon fibers and easy way of producing hydrogen.

The method according to the invention is suitable in different embodiments for producing different kinds of pyrolysis products and derivatives thereof and for producing energy fractions, such as heat energy.

The invention is not limited merely to the examples referred to above; instead, many variations are possible within the scope of the inventive idea defined by the claims. 

1. A method for carrying out pyrolysis in such manner that a first raw material is fed to a combustion boiler and a second raw material is fed to a pyrolysis reactor which are integrated together, energy fractions are formed from the raw material in the combustion boiler and gaseous and liquid product fractions are formed from the raw material in the pyrolysis reactor by fast pyrolysis, characterized in that production of the pyrolysis product and energy fractions is controlled by optimizing the selection of the raw material, the product distribution and the production costs, value and quality of at least one product fraction by varying the process variables, which are selected from the group comprising a first raw material, second raw material, quantities of the raw materials, selection of additional materials, process parameters, selection of an additional process step, composition and quantity of the carrier gas used, quantity of oxygen, selection of a heat transfer agent and moisture content of the raw material.
 2. The method according to claim 1, characterized in that the gaseous product fractions produced during the pyrolysis are mainly condensed to liquid pyrolysis products.
 3. The method according to claim 1 or 2, characterized in that the raw material is selected from the group comprising organic matter, chips, forest chips, wood, bark, sawdust, straw, coal, peat, oil, oil shale, lignite, petroleum, biomass, energy containing waste material, plastic, waste plastic, fuel containing waste, refuse derived fuel/RDF, pine oil, black lye, organic solvent and derivatives thereof.
 4. The method according to any one of claims 1 to 3, characterized in that the method comprises a multistep pyrolysis, wherein fast pyrolysis is performed as a first step and improved product fractions and/or additional product fractions are formed as a second step by applying an additional step.
 5. The method according to any one of claims 1 to 4, characterized in that the method comprises a multistep pyrolysis, wherein an additional step is performed as a first step and fast pyrolysis is performed as a second step in order to form improved product fractions and/or additional product fractions.
 6. The method according to claim 4 or 5, characterized in that the additional step is selected from the group comprising: drying, temperature raising step, gasification step, dust separation, reforming, steam reforming, separating the product fractions and separating the solids.
 7. The method according to any one of claims 1 to 6, characterized in that the realization of the pyrolysis step is modified in the method by at least one special operation, which is selected from the group comprising adjusting the temperature, selecting the carrier gas, feeding vapor and adding oxygen.
 8. The method according to any one of claims 1 to 7, characterized in that the carrier gas is selected from the group comprising combustion gas, water vapor, air and a mixture thereof.
 9. The method according to any one of claims 1 to 8, characterized in that the carrier gas contains oxygen.
 10. The method according to any one of claims 1 to 9, characterized in that additional oxygen is added to the carrier gas.
 11. The method according to any one of claims 1 to 10, characterized in that most of the side, residual and waste flows are circulated to the combustion boiler.
 12. The method according to any one of claims 1 to 11, characterized in that heat transfer material is used for transferring the energy fraction from the combustion boiler to a desired process step and/or recovery.
 13. The method according to any one of claims to 12, characterized in that the heat transfer material is selected from the group comprising sand, bed sand, aluminum oxide based material, other fluidization material and the like.
 14. The method according to any one of claims to 13, characterized in that the heat transfer material is circulated from the combustion boiler to the pyrolysis reactor and from the pyrolysis reactor to the combustion boiler via a separation step.
 15. The method according to any one of claims 1 to 14, characterized in that the process parameters are selected from the group comprising temperature of the pyrolysis step, temperature of the additional step, residence time in the pyrolysis reactor, temperature of the combustion boiler, way of mixing and order of mixing the raw materials of the pyrolysis, the carrier gas and the heat transfer material, addition of oxygen, circulation of the heat transfer material and circulation of the product and side fractions.
 16. The method according to any one of claims 1 to 15, characterized in that the first raw material and the carrier gas are arranged to a mixture and the heated heat transfer material is conducted to the mixture. 